Characteristics of reservoirs for inter-salt shale oil of Qianjiang Formation, Qianjiang Sag, Jianghan Basin: a case study of the Eq34-10 rhythm
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摘要: 江汉盆地始新统潜江组盐间页岩油是近年来研究的热点和难点。为了明确盐间页岩储层岩相及其储集物性,综合运用岩心观测、岩石薄片鉴定、X衍射、高压压汞和页岩孔渗等资料,对潜江凹陷潜江组盐间页岩油储层岩相发育特征及其对储集物性的影响进行了研究。该区盐间页岩油储层主要包括富碳纹层状泥质白云岩相、富碳纹层状云/灰质泥岩相和钙芒硝充填富碳纹层状云质泥岩相3种不同类型的岩相类型,前2种岩相的孔隙度明显高于后者。不同岩相孔径分布差异明显,富碳纹层状泥质白云岩相以孔径大于41 nm的孔隙为主,中值孔喉半径为219 nm;而富碳纹层状云/灰质泥岩相和钙芒硝充填富碳纹层状云质泥质相则以孔径小于41 nm的孔隙为主,中值孔喉半径为21 nm。富碳纹层状泥质白云岩相岩性均一,具有良好的储集空间和较大的孔喉结构,页岩储层中的含油性较高,为盐间页岩油储层中的优势岩相,是研究区最有利的页岩油勘探目标。Abstract: The inter-salt shale oil of the Eocene Qianjiang Formation in the Jianghan Basin is a hot and difficult research target in recent years. In order to clarify the lithofacies and physical properties of the inter-salt shale reservoirs, based on core observation, thin section observation, X-ray diffraction, high-pressure mercury intrusion and shale porosity and permeability analyses, a case study was carried out for the Qianjiang Formation in the Qianjiang Sag of Jianghan Basin. Results showed that there were three types of lithofacies, including carbonaceous laminar argillaceous dolomites, carbonaceous lamellar dolomitic/lime mudstones and carbonaceous lamellar dolomitic mudstones filled with glauberites. The porosities of the first two lithofacies were significantly higher than that of the latter. The pore size distribution of different lithofacies showed that the carbonaceous laminar argillaceous dolomites were dominated by pores with radius greater than 41 nm, and the median pore-throat radius was 219 nm, while the other two facies were dominated by pores with pore radius less than 41 nm and the median pore-throat radius was 21 nm. The carbonaceous laminar argillaceous dolomites were indicated to be homogeneous in lithology. As reservoir, they have good reservoir space, larger pore-throat structure and higher oil content, and was the dominant facies in the inter-salt shale oil reservoir and is promising to be the most favorable shale oil exploration target in the study area.
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图 4 江汉盆地潜江凹陷潜江组盐间页岩岩心扫描照片
图版上部为白光照片,下部为荧光照片。a.纹层状泥晶白云岩(2 813.7~2 816.2 m),纹层状灰质/云质泥岩(2 816.2~2 819.3 m);b.纹层状灰质/云质泥岩(2 819.3~2 820.43 m),含钙芒硝条带纹层状云质泥岩(2 820.43~2 823.78 m)
Figure 4. White light and fluorescence scanning photos of inter-salt shales in Qianjiang Formatiom, Qianjiang Sag, Jianghan Basin
表 1 江汉盆地潜江凹陷潜江组潜34-10韵律盐间页岩层矿物成分统计
Table 1. Mineral composition of inter-salt shales in Eq34-10 rhythm, Qianjiang Formation, Qianjiang Sag, Jianghan Basin
% 井号 黏土矿物 硬石膏 石英 钾长石 斜长石 方解石 白云石 菱铁矿 黄铁矿 石盐 钙芒硝 BX7 $ \frac{0.6 \sim 39.1}{20.7 /(72)}$ $\frac{0.3 \sim 17.1}{1.3 /(72)} $ $ \frac{3.8 \sim 15.6}{8.2 /(72)} $ $\frac{0.5 \sim 4.4}{1.1 /(72)} $ $\frac{1.6 \sim 7.1}{4.3 /(72)} $ $ \frac{2.7 \sim 50.8}{22.6 /(72)}$ $\frac{12.1 \sim 73.8}{31.8 /(72)} $ $ \frac{0.1 \sim 13.1}{0.6 /(72)}$ $\frac{1.9 \sim 12.6(72)}{7.1 /(72)} $ $ \frac{0.1 \sim 0.3}{0.2 /(72)}$ $ \frac{0.4 \sim 5.8}{2.2 /(72)}$ BYY1 $ \frac{0.1 \sim 33.3}{12.2 /(117)}$ $ \frac{0.4 \sim 41.2}{3.4 /(117)}$ $ \frac{0.1 \sim 15}{7.3 /(117)}$ $ \frac{0.2 \sim 10.6}{0.7 /(117)}$ $\frac{1.9 \sim 20}{6.7 /(117)} $ $ \frac{0.3 \sim 65.1}{10.9 /(117)}$ $\frac{2.0 \sim 70.3}{28.7 /(117)} $ $ \frac{0.0}{(117)}$ $\frac{1.0 \sim 28.2}{4.3(117)} $ $ \frac{0.6 \sim 92}{3.7(117)}$ $\frac{1.4 \sim 91.3}{18.5(117)} $ BYY2 $ \frac{1.5 \sim 42.3}{12.4 /(128)}$ $ \frac{0.1 \sim 0.6}{0.2 /(128)}$ $\frac{1.9 \sim 16.4}{6.7 /(128)} $ $\frac{0.2 \sim 9}{0.5 /(128)} $ $\frac{2.7 \sim 15.5}{7.1 /(128)} $ $ \frac{1.0-45.0}{9.8 /(128)}$ $ \frac{3.7 \sim 74.3}{30.9 /(128)}$ $\frac{0.0}{(128)} $ $\frac{1.1 \sim 32.8}{5.4(128)} $ $\frac{0.6 \sim 63.2}{3.0(128)} $ $ \frac{3.0 \sim 84.1}{23.4(127)}$ W99 $\frac{5.7 \sim 54.7}{26.7 /(54)} $ $\frac{0.0}{(57)} $ $\frac{2.6 \sim 17.6}{10.8 /(57)} $ $\frac{0.1 \sim 2.2}{0.3 /(57)} $ $\frac{0.2 \sim 5.6}{1.8 /(57)} $ $ \frac{1.5 \sim 39.8}{9.7 /(57)}$ $ \frac{2.8 \sim 76.9}{23.6 /(57)}$ $\frac{0.0}{(57)} $ $ \frac{1.5 \sim 9.3}{3.2(57)}$ $\frac{0.8 \sim 6.3}{1.5(57)} $ $\frac{3.6 \sim 82.5}{22.3(57)} $ 平均 16.0 1.4 7.8 0.7 5.7 12.6 29.3 0.1 5.1 2.5 17.6 注:表中数据意义为$\frac{ { 最小值 \sim 最大值 }}{\text { 平均值(样品数) }} $。 表 2 江汉盆地潜江凹陷潜江组潜34-10韵律盐间页岩储集物性数据
Table 2. Reservoir properties of inter-salt shales in Eq34-10 rhythm, Qianjiang Formation, Qianjiang Sag, Jianghan Basin
井号 孔隙度/% 渗透率/10-3 μm2 BX7 1.9~9.1/6.0(18) 0.06~1.6/0.55(18) BYY1HF 4.1~10.2/8.5(65) 0.13~3.6/1.5(40) BYY2 5.1~18/11.9(78) 0.23~5.1/2.18(47) W99 14.2~31.3/22.(4) 0.7~1.3/1.0(2) 注:表中数据意义为:最小值~最大值/平均值(样品数)。 -
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